fixmul

Section: Allegro manual (3)
Updated: version 4.2.2
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NAME

fixmul - Multiplies two fixed point values together. Allegro game programming library.  

SYNOPSIS

#include <allegro.h>

fixed fixmul(fixed x, fixed y);  

DESCRIPTION

A fixed point value can be multiplied or divided by an integer with the normal `*' and `/' operators. To multiply two fixed point values, though, you must use this function.

If an overflow occurs, `errno' will be set and the maximum possible value will be returned, but `errno' is not cleared if the operation is successful. This means that if you are going to test for overflow you should set `errno=0' before calling fixmul(). Example: 

   fixed result;
   
   /* This will put 30000 into `result'. */
   result = fixmul(itofix(10), itofix(3000));
   /* But this overflows, and sets `errno'. */
   result = fixmul(itofix(100), itofix(3000));
   ASSERT(!errno);
 

RETURN VALUE

Returns the clamped result of multiplying `x' by `y', setting `errno' to ERANGE if there was an overflow.

 

SEE ALSO

fixadd(3), fixsub(3), fixdiv(3), ex3buf(3), excustom(3), exfixed(3), exspline(3), exstars(3), exupdate(3)